Embodiments of the invention relate generally to a solid-state photomultiplier (SSPM) and more particularly to a signal-to-noise ratio optimized solid-state photomultiplier module.
Currently, vacuum photomultiplier tubes (PMTs) are used in various applications such as Laser gel and blot scanners, confocal microscopes, and two-photon microscopes. Unfortunately, these PMTs are expensive and generally provide low performance with respect to detection efficiency. In certain examples, SSPMs have been used in place of PMTs in an effort to reduce cost.
Traditionally, solid-state photomultipliers (SSPMs) include a photo sensor with an array of photodiodes operating above their breakdown voltage, typically known as a Geiger mode. These arrays of photodiodes may be referred to as Geiger photodiodes (GPDs). SSPMs are capable of achieving the low noise of a PMT at a low cost while retaining the high quantum efficiency of a silicon device. The SSPMs include a scintillating material that illuminates upon a reception of energy. The array of photodiodes detect illumination of the scintillating material. Since the light produced in the scintillation material is proportional to the energy of the absorbed event, the number of pixels that are activated provide the energy of the incident photon when the SSPM is uniformly illuminated.
Although SSPMs have several advantages over PMTs, there are two major technical challenges associated with SSPMs. SSPMs have a high dark count rate that may become a non-negligible source of noise. Another disadvantage of SSPMs relate to their limited number of microcells which include photodiodes connected to a quenching resistor. The limited number of microcells restrict the dynamic range of the corresponding SSPM. These disadvantages may be particularly undesirable in applications that typically require wider dynamic range and efficient detection at lower concentration or light levels, such as Laser gel and blot scanners.
It is therefore desirable to improve the dynamic range and reduce the dark count rate of the SSPM to achieve increased detection efficiency.